RJ,
One of the interesting things about plane design is that sometimes the
"odd" design works better than the intended plane! So what you are asking
for is really an "engineer's" plane, not a flying plane.
What do I mean by that? Well take airfoils. Even if CNC machined and
then polished by extremely accurate methods, the airfoils are not going to
be 100%. It simply costs too much to get that kind of accuracy. So there
will be some sort of error, no matter how small, that will be in every
plane. A couple of swipes too much here or there could give .01 in error
either way with little knowledge! That can change things dramatically....or
does it?
Every (well almost every) plane that goes to market has a certain design
plan when they start. Say a RG-15 equipped F3b model (I am using this for a
reason). So off goes the manufacturer, they make the molds, polish for
hours and hours, and finally start making planes. Several test planes go
out and finally a plane that flies like X goes out. X is a series of
properties the plane has...say turns well, little slow in straight, likes
ballast, and thermals well. Everyone reads this, hears excerpts, and then
eventually flies them.
Notice I never mentioned to check the exact airfoil? Well to be honest,
it is not needed. The plane may not be perfect, but it flies like that
plane flies <G>. There is a great example of this for F3b. The Diamond.
Checking the airfoil shows that the RG-15 airfoil is a bit fat. Like 1% too
big! Wow! Yet this plane flies great, is very fast, and has shown to be a
great performer. Why? Well who knows, but that combo works. Would a
perfect RG-15 work? Who knows...but the plane has a modified RG-15.
PErsonally I think that is why so many "modified xXX airfoils" are out
there. Screwups and the mfgr wants to protect themselves from people who
instead of flying will measure the plane then complain that the airfoil is
not perfect. Sorry, but it really does not matter, and perfection is rarely
an issue with our planes.
BTW - why are molded planes so expensive? Well...perhaps it is the
extensive labor costs needed to make one. Approx double the time it takes
to make a foam/carbon plane. So while they may be expensive, it is the
labor costs that dictate most of that expense. Of course the $4-10,000
spent to make the molds, polish them, and design them is also factored in.
Jason Werner
----- Original Message -----
From: "RJ Steinhaus" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, August 11, 2000 3:39 PM
Subject: [RCSE] Measuring Conformance of Composite Wings
> I would like to know if there are any manufacturers that routinely do
> quality control on their composite wing manufacture to determine how
closely
> their products conform to the specified airfoil? Dr. Michael Selig made
> graphs in Soartech 8 "Airfoils at Low Speeds" of the conformance of the
wind
> tunnel models used in the generation of his performance information for
> studied airfoils. In that study Dr. Selig used a Hemel Checkmaster
> Coordinate Measuring Machine. This machine was capable of checking the
> absolute accuracy of the wing surface to at least 0.0005" (many of the
wind
> tunnel models diverged significantly from perfect conformance to the
desired
> airfoil). Do the molded wing manufacturers "close the loop" doing checks
on
> accuracy/quality or is everyone just doing "best effort" manufacture? Has
> anyone made a simplified airfoil profile measurement tool implemented with
> two digitizing travel gauges that can be clamped on an existing wing at
> various points to survey wing top and bottom surface airfoil profile
> conformance (this measurement may not reveal washout, wing twists or
warps,
> etc.). The costs of the molded aircraft are relatively high and it would
be
> nice to have knowledge that the wings of individual models are being
> manufactured accurately.
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